1. Field of the Invention
The present invention relates to a system for mounting a circuit component such as an electric-circuit or an electronic-circuit component on a circuit substrate such as a printed circuit board.
2. Related Art Statement
There are known various types of circuit-component ("CC") mounting systems.
For example, Japanese Patent Application laid open for opposition under Publication No. 2(1990)-53954 discloses a CC mounting system which includes a plurality of component holders, a holder revolving device which revolves the component holders around a vertical common axis line, a CC supplying device which supplies CCs, and a circuit-substrate ("CS") supporting device which supports a CS.
The holder revolving device includes (a) a rotatable body which is rotatable about the vertical axis line and which holds the plurality of component holders on a circle whose center rides on the axis line, such that the component holders are equiangularly spaced from each other about the center of the circle, i.e., the axis line; and (b) an intermittently rotating device which intermittently rotates the rotatable body such that the rotatable body is continuously rotated by a predetermined intermittent-rotation angle in a first step and then is stopped in a second step and the first and second steps are repeated. The intermittent-rotation angle is equal to a predetermined regularly-spacing angle at which the component holders are equiangularly spaced from each other about the vertical axis line. As the rotatable body is intermittently rotated about the axis line, the component holders are sequentially stopped at each of the same number of stop positions as the number of the component holders. Those stop positions include a CC receiving position where each of the component holders receives a CC from the CC supplying device, and a CC mounting position where each component holder mounts the CC on a CS supported by the CS supporting device. The CC supplying device includes a plurality of CC supplying cartridges which are set on a movable table such that respective CC supplying portions of the CC supplying cartridges are arranged along a straight line. When the movable table is moved by a table moving device in a direction parallel to the above straight line, one of the CC supplying cartridges is moved to, and positioned at, a CC supplying position, that is, the CC receiving position. The CS supporting device currently positioning and supporting the CS is moved by a CS moving device to appropriate positions in a horizontal plane, so that a plurality of CC-mount places on the CS where CCs are mounted are positioned, one by one, at the CC mounting position at which the component holders are positioned one by one. Thus, each component holder mounts a CC at a CC-mount place on the CS at the CC mounting position. In this CC mounting system, the plurality of component holders can successively reach the CC receiving or mounting position, at a short interval of time, so that each component holder receives or mounts a CC.
In this CC mounting system, however, it is required to move the movable table supporting the CC supplying cartridges, and the CS supporting device positioning and supporting the CS. Since the movable table and the CS supporting device are of a large size, a large space is needed for allowing the movement of each of the table and the supporting device, which leads to increasing the overall size of the CC mounting system. Meanwhile, the movable table of the CC supplying device and the CS supporting device are provided at respective positions where the movement of one of the two elements does not interfere with the movement of the other element. However, the CS must be moved such that all the CC-mount places thereon are moved to the CC mounting position where the component holders are sequentially positioned, that is, the CS must be moved in a wide area, which leads to increasing the distance between the CC receiving position and the CC mounting position which is prescribed at the center of a range in which the CS is moved in a direction in which the CC supplying device and the CS supporting device are arranged. Thus, it is difficult to reduce the size of the rotatable body and accordingly is difficult to increase the speed of intermittent rotation of the rotatable body.
Japanese Patent Application No. 6(1994)-196546 discloses another CC mounting system which includes a rotatable body which holds a plurality of component holders and which is intermittently rotatable about a vertical axis line, and a moving device which moves the rotatable body to a desired position in a horizontal plane, so that the component holders take CCs from a CC supplying device which is provided at a fixed position, and mount the CCs on a CS. The component holders are held by the rotatable body such that each component holder is moved up and down, and the rotatable body is equipped with a plurality of elevating and lowering devices each of which elevates and lowers a corresponding one of the plurality of component holders between its lower, operative position where the one component holder receives and mounts a CC and its upper, inoperative position where the one holder does not. The elevating and lowering devices are supported on a support member which is fitted in the rotatable body such that the support member is not rotatable about its axis line, and is movable in its axial direction, relative to the rotatable body. When the support member is lowered in the state in which one of the elevating and lowering devices holds a corresponding one of the component holders at its operative position, the one component holder as a selected component holder receives and mounts a CC.
In the second CC mounting system, as the rotatable body is intermittently rotated, the plurality of component holders are sequentially positioned at a CC receiving position, as one of the plurality of stop positions, where each component holder receives a CC and, after all the component holders receive CCs, respectively, the rotatable body is moved to above the CS, for mounting the CCs on the CS. However, the component holders have no predetermined CC mounting position, that is, each of the component holders can mount a CC on a CS at any one of the stop positions on the locus of revolution of the holders. Since the plurality of elevating and lowering devices are provided for the plurality of component holders, respectively, each component holder can mount a CC at any stop position.
The second CC mounting system enjoys various advantages. For example, since the second system does not need any movement of a support table supporting CC supplying cartridges, or any movement of a CS supporting device supporting a CS, the second system does not need any large space for allowing the large-size support table or the large-size CS supporting table to move, which contributes to reducing the overall size of the second system. This advantage is maximized in those particular cases where many sorts of CCs are supplied from many CC supplying cartridges or where large-size CSs are used, because no large is needed for allowing a large-size support table supporting the CC supplying cartridges or a large-size CS supporting device supporting a large-size CS to move. In addition, since the CC supplying device and the CS supporting device can be arranged side by side with substantially no clearance being provided therebetween, the second system can enjoy a compact construction.
Moreover, since the rotatable body of the second system is just required to have a size sufficient to support the component holders, it can be smaller than that of the first system disclosed in the above-identified Japanese document No. 2-53954. Accordingly, it is possible to increase the speed of intermittent rotation of the rotatable body and thereby shorten a cycle time between the time when the preceding one of adjacent two component holders finishes its CC holding or mounting operation and the time when the following component holder finishes its CC holding or mounting operation. The more component holders the second system employs, the more benefit the second system gains from shorting the above cycle time.
However, the second system disclosed in the above-identified Japanese document No. 6-196546 has no predetermined CC mounting position, which leads to increasing the time needed for mounting CCs on a CS, because the rotatable body must be moved by not only the distance between two CC-mount places on the CS where two CCs are successively mounted but also the distance between two component holders holding the two CCs. Meanwhile, in the case where each component holder receives and mounts a CC at different stop positions, respectively, the angular or rotation position of the CC received by each component holder at one stop position is changed to a different rotation position of the CC when each component holder mounts the CC at another stop position. If the rotatable body is rotated for correcting the rotation position of each CC, such rotation may lead to increasing the distance of movement of the rotatable body and thereby increasing the time needed for mounting CCs. Even if each CC may have no need to correct its rotation position, the rotatable body may be rotated for changing the position of the CC in a horizontal plane, and thereby moving the CC nearer to a position corresponding to a CC-mount place on the CS. However, this rotation results in changing the current rotation position of each CC, and additionally it is difficult to calculate the distance by which the moving device moves the rotatable body.